Recently, ultrasonic diagnosis apparatuses have been widely used in the general medical field. An ultrasonic diagnosis apparatus allows real-time visual recognition of, for example, the pulsation of the heart of an object and the movement of a fetus with the simple operation of only bringing an ultrasonic probe into contact with the body surface of the object. The ultrasonic diagnosis apparatus is considered highly safe for human bodies, and can be repeatedly used for examination.
In addition, the ultrasonic diagnosis apparatus is smaller in system size than other medical image diagnosis apparatuses such as an X-ray diagnosis apparatus, CT apparatus, and MRI apparatus. Therefore, for example, this apparatus allows easy examination upon being moved to a bed side. More specifically, although it depends on the types of functions of the ultrasonic diagnosis apparatuses, for example, compact apparatuses which can be carried with, for example, one hand have been developed.
As described above, the ultrasonic diagnosis apparatus is free from the influence of exposure to radiation and the like and is small in size, and hence can be used for home medical care services and the like.
The ultrasonic diagnosis apparatus has a problem of so-called speckle noise caused by simultaneous occurrence of reflection and scattering of ultrasonic waves due to a medium, small bioligical tissue, or the like in an object. This speckle noise degrades not only the image quality of a video but also accuracy in the display of an important form such as the boundary between a body organ to be observed and the background. Such speckle noise is a significant trouble in fields of video interpretation, organ recognition, and the like using videos acquired by the ultrasonic diagnosis apparatus.
In order to solve this problem, for example, the following technique is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2006-116307.
That is, Jpn. Pat. Appln. KOKAI Publication No. 2006-116307 discloses a technique including a step (a) of decomposing a two-dimensional ultrasonic input video into a plurality of multiresolution videos at N (a positive integer) levels, a step (b) of determining the characteristic of each pixel of each decomposed video, a step (c) of executing image quality improvement processing for each decomposed video based on the pixel characteristics, a step (d) of executing 1-level composition of the decomposed videos, and a step (e) of repeatedly executing the steps (b) to (d) until the size of the composite video becomes equal to that of the above two-dimensional ultrasonic video. More specifically, wavelet transform is used for multiresolution analysis used in the step (a).
The technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2006-116307 removes speckle noise and hence improves the image quality of a video acquired by the ultrasonic diagnosis apparatus.
The ultrasonic diagnosis apparatus performs imaging by transmitting ultrasonic waves from the ultrasonic probe to the inside of an object and receiving reflected signals from the inside of the object. For this reason, in the process of propagation of ultrasonic waves in an object, for example, ultrasonic waves are scattered or attenuated. That is, the deeper a region is located in an object, the more difficult to visualize it by the ultrasonic diagnosis apparatus.
More specifically, the distance resolution is superior but the depth sensitivity is inferior when the wave train length of the transmission waveform of an ultrasonic wave is short than when the wave train length is long. In addition, the higher the frequency of an ultrasonic wave, the higher the spatial resolution. However, since the degree of attenuation of the ultrasonic wave during propagation increases, the depth sensitivity decreases.
The same applies to contrast-enhanced ultrasonography. In contrast-enhanced ultrasonography, the detection sensitivity of contrast-enhanced bubbles is obviously important. The ability to visually recognize contrast-enhanced bubbles with high spatial resolution is also important in a clinical point of view because, for example, it facilitates visual recognition of the marginal information of a lesion.
As described above, in the ultrasonic diagnosis apparatus, there exists the so-called tradeoff between the sensitivity of an acquired video and the resolution, and it is very difficult to satisfy both the requirements.
Note that the technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2006-116307 is not a technique that solves this problem.
The present invention has been made in consideration of the above situation, and has as its object to provide an ultrasonic diagnosis apparatus and program which can acquire a video that satisfies both the requirements for sensitivity (luminance) and resolution (visibility).